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This article in JEQ

  1. Vol. 31 No. 6, p. 1901-1909
     
    Received: Oct 16, 2001


    * Corresponding author(s): haha@kvl.dk
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doi:10.2134/jeq2002.1901

pH-Dependent Release of Cadmium, Copper, and Lead from Natural and Sludge-Amended Soils

  1. Orathai Sukreeyapongsea,
  2. Peter E. Holmb,
  3. Bjarne W. Strobelb,
  4. Supamard Panichsakpatanaa,
  5. Jakob Magidb and
  6. Hans Christian Bruun Hansen *b
  1. a Dep. of Soil Science, Kasetsart University, Phaholyathin, Chatujak, Bangkok, 10900, Thailand
    b Dep. of Agricultural Sciences, The Royal Veterinary & Agricultural University, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark

Abstract

The pH-dependent release of cadmium, copper, and lead from soil materials was studied by use of a stirred flow cell to quantify their release and release rates, and to evaluate the method as a test for the bonding strength and potential mobility of heavy metals in soils. Soil materials from sludge-amended and nonamended A horizons from a Thai coarse-textured Kandiustult and a Danish loamy Hapludalf were characterized and tested. For each soil sample, release experiments with steady state pH values in the range 2.9 to 7.1 and duration of 7 d were performed. The effluent was continuously collected and analyzed. Release rates and total releases were higher for the Hapludalf than the Kandiustult and higher for the sludge-amended soils than the nonamended soils. With two exceptions the relative release rates (release rate/total content of metal in soil) plotted vs. steady state pH followed the same curves for each metal, indicating similar bonding strengths. These curves could be described by a rate expression of the form: relative release rate = k[H+] a , with specific a (empirical constant) and k (rate constant) parameters for each metal demonstrating that metal release in these systems can be explained by proton-induced desorption and dissolution reactions. With decreasing pH, pronounced increases in release rates were observed in the sequence cadmium > lead > copper, which express the order of metal lability in the soils. The flow cell system is useful for comparison of metal releases as a function of soil properties, and can be used as a test to rank soils with respect to heavy metal leaching.

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Copyright © 2002. American Society of Agronomy, Crop Science Society of America, Soil Science SocietyPublished in J. Environ. Qual.31:1901–1909.